756 research outputs found

    Time-Staging Enhancement of Hybrid System Falsification

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    Optimization-based falsification employs stochastic optimization algorithms to search for error input of hybrid systems. In this paper we introduce a simple idea to enhance falsification, namely time staging, that allows the time-causal structure of time-dependent signals to be exploited by the optimizers. Time staging consists of running a falsification solver multiple times, from one interval to another, incrementally constructing an input signal candidate. Our experiments show that time staging can dramatically increase performance in some realistic examples. We also present theoretical results that suggest the kinds of models and specifications for which time staging is likely to be effective

    The unintended consequences of a complex intervention combining performance-based financing with health equity measures in Burkina Faso

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    Contexte : La mauvaise qualité et la faible utilisation des services de santé contribuent aux taux élevés de morbidité et de mortalité dans plusieurs pays à faible et à moyen revenu. Face à cette situation, le gouvernement du Burkina Faso a testé une intervention novatrice qui combine le financement basé sur la performance (FBP) à des mesures d'équité en santé. Les formations sanitaires ont reçu des prix unitaires pour des services de santé fournis ainsi que des bonus conditionnels à la qualité des soins. Des comités communautaires ont sélectionné les indigents pour leur octroyer des exemptions de paiements des soins. Malgré le peu d’études sur le sujet, des acteurs en santé mondiale craignent que l’intervention puisse avoir des conséquences non intentionnelles importantes. Objectif : Cette thèse vise à accroître les connaissances scientifiques sur les conséquences non intentionnelles du FBP combiné à des mesures d'équité en santé dans un environnement à faible revenu. Méthodes : Nous avons développé un cadre conceptuel basé sur la théorie de la diffusion des innovations. Une étude de cas multiples a été réalisée avec neuf formations sanitaires au Burkina Faso. Cinq mois sur le terrain ont permis d’effectuer 104 entrevues semi-structurées, 266 séances d'observation et des conversations informelles avec un large éventail d'acteurs incluant les prestataires de soins, les patients et les vérificateurs. Les données qualitatives ont été codées avec QDA miner pour faciliter l’analyse thématique. Nous avons également utilisé des données quantitatives du système de gestion pour décrire l'évolution des services et trianguler les résultats. Résultats : La nature et la mise en œuvre de l'intervention ont interagi avec le système social et les caractéristiques de ses membres pour engendrer des conséquences non intentionnelles importantes, dont la plupart étaient indésirables. Les prestataires de soins ont démontré une fixation sur les mesures de rendement, ont falsifié les registres médicaux et ont enseigné de mauvaises pratiques aux stagiaires pour augmenter leurs subsides et bonus. Comme conséquence non intentionnelle désirable, certaines formations sanitaires ont limité la vente de médicaments sans prescriptions pour encourager les consultations. Les vérifications communautaires, durant lesquelles les patients sont retrouvés pour vérifier les services déclarés, ont entraîné la falsification des données de vérification, la perte de la confidentialité des patients et certaines craintes chez les patients, bien que certains étaient heureux de partager leurs opinions. Enfin, les prestataires de soins ont limité les services offerts gratuitement aux indigents, ce qui a déclenché des conflits. Discussion : Cette thèse contribue au développement des connaissances scientifiques sur la façon dont le FBP, combiné à des mesures d'équité, peut engendrer des conséquences non intentionnelles. Les résultats sont utiles pour affiner ce type d’intervention et éclairer une mise en œuvre efficace dans le secteur du financement de la santé. Plus largement, cette thèse démontre la faisabilité et la valeur ajoutée d'utiliser un cadre conceptuel pour étudier les conséquences non intentionnelles. Elle pourra guider les chercheurs à élargir leur angle d’analyse afin de rendre compte des conséquences intentionnelles et non intentionnelles des interventions complexes en santé.Background: Poor quality and low utilization of healthcare services contribute to high levels of morbidity and mortality in many low- and middle-income countries (LMICs). In response, the government of Burkina Faso tested an innovative intervention that combines performance-based financing (PBF) with health equity measures. Healthcare facilities received unit fees for targeted services and bonuses conditional upon the quality of care. To reduce inequities in access to care, community-based committees selected indigents, i.e., the poorest segment of the population, to offer them user fee exemptions. Facilities were also paid more for services delivered to indigents. Despite the potential of this type of intervention, many global health actors argue that it could lead to important unintended consequences that influence its overall impact. Yet, little attention has been given to studying the unintended consequences of this complex intervention. Objective: This thesis aims to increase the scientific knowledge on the unintended consequences of PBF combined with health equity measures in a low-income setting. Methods: We developed a conceptual framework based on the diffusion of innovations theory. Using a multiple case study design, we selected nine healthcare facilities in Burkina Faso. Over five months of fieldwork, we collected multiple sources of qualitative data including 104 semi-structured interviews, 266 recorded observation sessions, informal conversations and documentation. Participants included a wide range of stakeholders, such as providers, patients, and PBF verifiers. Data were coded using QDA miner to conduct a thematic analysis. We also used secondary data from the PBF routine management system to describe the evolution of services and triangulate results. Results: Interactions between the nature and implementation of the intervention, the nature of the social system, and its members’ characteristics led to important unintended consequences, most of which were undesirable. Providers were fixated on performance measures rather than on underlying objectives, falsified medical registers, and taught trainees improper practices to increase subsidies and bonuses. As a desirable unintended consequence, we found that some facilities limited the sale of non-prescribed medication to encourage patients to consult. Community verifications, in which patients are traced to verify the authenticity of reported services and patient satisfaction, also led to unintended consequences, such as the falsification of verification data, the loss of patient confidentiality, and fears among patients, although some were pleased to share their views. Lastly, health equity measures also triggered changes that were not intended by program planners. For example, providers limited the free services and medication delivered to indigents, which led to conflicts between parties. Discussion: This thesis contributes to the development of scientific knowledge on how PBF interventions, combined with equity measures, can trigger unintended consequences in a low-income setting. The results are useful to inform effective implementation and refine interventions, particularly in the health financing sector. More broadly, this thesis demonstrates the feasibility and added value of using a conceptual framework to study the unintended consequences of complex health interventions. This thesis can inspire and guide future researchers to broaden their analytical horizons to capture both intended and unintended consequences of health interventions

    Opera as Statecraft in Soviet Armenia and Kazakhstan

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    This dissertation reconceptualizes Soviet music history by focusing on the artistic productions of ethnic and racial minorities under the Communist Party’s subjugation. According to communist propaganda, the Soviet state overthrew Russian imperialism and—as part of a cultural revolution—commissioned national operas to celebrate the diversity of each republic. I argue, however, that under the guise of modernization, the allegedly anti-colonial Communist Party used opera as a colonial technology of rule to negate difference. The Soviet national opera project thus pursued the age-old Russian imperial practices of assimilation and subjugation, which allowed communists to maintain rule over a multiethnic population. Each of the chapters focuses on one of the four intersecting axes across which the Soviet state attempted to redefine Armenian and Kazakh nationalism through opera: religious practices, historical memory, racialization, and gender norms. In addition to examining opera as an instrument of totalitarian control, as many scholars have done, a key feature of my work is the reversal of “the imperial gaze.” I propose a theory of drastic hybridity to examine how Armenian and Kazakh composers negotiated their identities in creative and subversive ways. The interdisciplinarity of this project—spanning music studies, Slavic studies, and postcolonial studies—charts new paths for remapping the geopolitics of Soviet history, which in turn allows us to understand the present-day struggle of Armenian and Kazakh peoples to decolonize their cultural identities

    Implications of Chronic Kidney Disease on presentation, treatment and outcomes in patients with Aortic Stenosis

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    Background Aortic valve stenosis (AS) is the most common valvular heart disease in the western world. No pharmacological treatment has been proved to halt the progression to severe disease and after symptom debut, the prognosis is poor with a high mortality, if left untreated. Hence, surgical or transcatheter aortic valve replacement (AVR) is the only therapeutic option for severe AS. AS is prevalent with rapid evolution among patients with chronic kidney disease (CKD). Concomitant AS and CKD is accompanied with high risk of death and cardiovascular events. The aims of this thesis were to: 1. Assess whether CKD is associated with the risk of developing AS in a general population 2. Determine the risk factors of worsening renal function following transcutaneous AVR (TAVR) and its association with the short and long-term mortality 3. Evaluate the point prevalence of AS and AVR at dialysis start, and to assess the incidence rates and associated risk factors for new onset AS after dialysis initiation. 4. Compare the long-term complication rates after surgical AVR (SAVR) with mechanical (MAV) or bioprosthetic aortic valve (BAV) in dialysis patients Methods and results Study I: Kidney Dysfunction and the risk of developing Aortic stenosis The study included all adult Stockholm citizens from the Stockholm CREAtinine Measurement project (SCREAM) with known kidney function and without prior diagnosis of AS, and the aim was to study the risk of AS in relation to kidney function. Kidney dysfunction was found to be independently associated with higher risk of developing AS. This risk increased linearly with lower estimated Glomerular Filtration Rate (eGFR) and was present after adjustments of covariates. Study II: Risk factors for worsening renal function and their association with long-term mortality following transcatheter aortic valve implantation: data from the SWEDEHEART registry We used the The SWEdish traNscatheter cardiac intervention regisTRY (SWENTRY), part of Swedish Web-system for Enhancement and Development of Evidence -based care in Heart disease Evaluated According to Recommended Therapies (SWEDHEART) to identify all patients with severe AS who underwent TAVR. Risk factors associated with persistent acute kidney injury (pAKI) were explored, and their association to short- and long-term mortality was explored. pAKI occurred in 6.1% of AS patients who underwent TAVR and was associated with a doubled short- and long-term risk of death, independent of baseline kidney function. Male gender, baseline kidney function and transapical access were found to be independently associated with pAKI. Study III: Epidemiology of aortic stenosis/aortic valve replacement in the nationwide Swedish Renal Registry The Swedish Renal Registry (SNR), a national registry of all patients who commenced dialysis or received a kidney transplant in Sweden between 1993 and 2018, was used to identify the point prevalence of AS and AVR at dialysis start, and to explore the incidence and associated factors for developing AS and AVR after dialysis initiation. We found that patients initiating dialysis have high prevalence and occurrence of AS. Older age, male gender, hypertension, and peritoneal dialysis were strongly associated with new onset AS. Only 20% of new cases with incident AS underwent AVR. Study IV: Prognosis after aortic valve replacement in dialysis patients – a report from the Swedish Renal Registry We identified all dialysis patients in the SNR registry who had undergone surgical AVR with MAV or BAV. We compared the long-term complication rates of the composite end-point of all-cause death, bleeding, stroke and aortic valve reoperation, and separately, the end-point all-cause death. The main finding was that BAV- and MAV-recipients had comparable mortality and complication rates. Conclusions Kidney dysfunction is independently associated with new onset AS in a general population. This association was attenuated, but remained significant after adjustments, and the association increased linearly with lower eGFR categories. In unselected patients with severe AS undergoing TAVR, worsening kidney function occurred often, and was predicted by male gender, baseline kidney dysfunction and access type. pAKI was strongly associated with higher risk of all-cause death. Among dialysis patients, the prevalence at initiation and occurrence of clinically detected AS was high, but few underwent AVR. Dialysis patients who underwent surgical AVR with MAV or BAV had similar rates of all-cause death and overall complication rates

    A Monte Carlo approach to statics and dynamics of quantum fluids

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    The main objective of the thesis is to study static and/or dynamic properties of a set of quantum fluids by means of quantum Monte Carlo techniques, mainly using the path integral formalism to obtain results both at zero temperature and finite temperature. First, we present briefly some of the more important quantum Monte Carlo methods, and introduce the Path Integral Monte Carlo (PIMC) method, which has been used during all this thesis, as well as the Path Integral Ground State (PIGS), which is an extension of the first at ground state. After introducing the basic formalism, we comment on the approximations needed and provide a comparison between different actions. We also comment on parallelization schemes and advanced sampling techniques. The first results shown in this thesis are for the phase diagram of a one-dimensional Coulomb gas, which have been obtained using the PIMC method. The phase diagram have been constructed mainly by calculating energetic and structural properties. The obtained results extend previous knowledge of different phases in the one-dimensional Coulomb gas at zero temperature. Our results show the existence of a quantum Wigner crystal regime and a Ideal Fermi gas regime at low temperatures. As temperature increases, we reach a classic Wigner crystal regime and a classical gas. In the following chapter we show the results of a quasi-one-dimensional para-H2. The aim of this work is to see how the quasi-one-dimensionality affects the Luttinger parameter when comparing it with the pure one-dimensional case. This is done at zero temperature using PIGS. As para-hydrogen is an important candidate to superfluidity, the main idea behind study a quasi-one-dimensional system is to reduce dimensionality in order to soften intermolecular interaction. For that, we try different external potentials to control the opening of the system in two dimensions. Despite an increase in the Luttinger parameter in the various quasi-one-dimensional cases, it still does not reach the values displaying superfluidity. The next work shown in the thesis is our extensive study of the dynamic structure factor for the 4He. Using Path Integral Monte Carlo, we compute the intermediate scattering function at different temperatures and perform an inversion in order to gain access at the dynamics of the system. Despite the ill-posed problem of this inversion, we obtain results in a qualitative agreement with the experiments and prove that our method of inversion, despite having to yield with inversion problems achieves to obtain better numerical results for 4He at finite temperature than the ones previously reported. In this sense, we provide comparisons with the Maximum Entropy method and with experimental results. The study at different temperatures shows us the dissappearance of the roton peak when we cross T=2.17K from the superfluid regime to the normal fluid. We also observe a kink in the momentum distribution at the superfluid regime that dissappears at higher temperatures, for which does not exist an explanation in the theory. In the final chapter of the thesis we provide a method to sample complex-time correlation functions whose aim is to obtain better dynamic structure factor functions than the ones obtained via pure imaginary-time correlation functions. This model has already been tested for single-particle systems. Our aim is to test it for multi-particle systems, and to see if we can still recover good results at a reasonable high complex-time when the number of particles is closer to the typical simulation values of real systems. We tested it with particles interacting with an harmonic potential. Despite an increased variance compared with the one-particle case, we obtain good results that allow us to obtain the dynamic structure factor. Comparing the results with ones obtained at pure-imaginary time, we show how the complex-time inversion is superior and provides results closer to the exact ones.L'objectiu principal d'aquesta tesi es l'estudi de propietats estàtiques i dinàmiques de diferents fluids quàntics utilitzant tècniques de Monte Carlo quàntiques, principalment emprant el formalisme de path integrals per obtenir resultats tan a temperatura zero com a temperatura finita. Primer de tot, presentem els mètodes de Monte Carlo quàntics més importants, i introduïm el mètode de Path Integral Monte Carlo (PIMC), que fem servir al llarg de tota la tesi, i el mètode de Path Integral Ground State (PIGS), que es una extensió del primer però a temperatura zero. Després d'introduir el formalisme bàsic, comentem les diferents aproximacions necessàries i aportem una comparació entre elles. També expliquem un possible mètode de paral·lelització i tècniques de mostreig avançat. Els primers resultats que mostrem en aquesta tesi son pel diagrama de fases d'un gas de Coulomb unidimensional, que hem obtingut emprant PIMC. Hem construït el diagrama de fases mitjançant el càlcul de propietats energètiques i estructurals. Els nostres resultats amplien estudis previs que s'havien realitzat pel mateix sistema a temperatura zero. Els nostres resultats mostren l'existència d'un règim de cristall de Wigner quàntic i un d'un gas de Fermi ideal a temperatures baixes. Incrementant la temperatura obtenim un cristall de Wigner clàssic i un gas clàssic. En el següent capítol ensenyem els resultats per un sistema quasi-unidimensional de parahidrogen. L'objectiu d'aquest estudi es veure si la quasi-unidimensionalitat afecta al paràmetre de Luttinger quan el comparem pel cas purament unidimensional. Això ho fem a temperatura zero utilitzant PIGS. Sent el parahidrogen un fort candidat a ser superfluid, la idea principal es veure si reduint la dimensionalitat del sistema podem alleugerir suficient la interacció intermolecular. Per fer-ho, provem diferents potencials externs per controlar l'obertura del sistema en dues de les dimensions. Tot i l'increment del paràmetre de Luttinger respecte al cas unidimensional, aquest no arriba als valors esperats per mostrar superfluïdesa. El següents resultats són del nostre estudi sobre el factor d'estructura dinàmic per 4He. Utilitzant PIMC, calculem la funció de dispersió a diferents temperatures i fem una inversió per tal d'accedir a les propietats dinàmiques del sistema. Tot i la naturalesa de problema mal posat d'aquesta inversió, obtenim resultats qualitativament bons en comparació amb els experimentals, i provem que el nostre mètode d'inversió obté resultats superiors per 4He a temperatura finita que els obtinguts prèviament utilitzant altres mètodes. En aquest sentit, aportem una comparació amb el mètode de màxima entropia i amb resultats experimentals. L'estudi a diferents temperatures ens deixa veure la desaparició del pic del rotó quan creuem T=2.17K des de el règim superfluid al fluid normal. També observem una curvatura estranya en la distribució de moments en el règim de superfluïdesa que desapareix a temperatures més elevades, i pel qual no existeix cap explicació teòrica. Finalment, mostrem un mètode per calcular funcions de correlació en temps complex, l'objectiu del qual es obtenir factors d'estructura dinàmic superiors als obtinguts en temps purament imaginari. Aquest model ha sigut provat amb èxit en sistemes d'una sola partícula. El nostre objectiu es veure si obtenim resultats bons en sistemes amb més partícules, i si el temps complex màxim al que podem accedir no es redueix amb aquest increment. Tot i l'increment en la variança, obtenim bons resultats pel factor dinàmic i, comparant-los amb els obtinguts amb temps imaginari, podem veure com el temps complex ofereix resultats més pròxims als exactes
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